8. Divisions of Logic. -- (1) It is usual to divide logic into two branches: formal and real logic. This division, which is of relatively recent date, is very questionable:

(a) It is. obviously inspired by certain arbitrary theories of Kant's philosophy.^{1}

(b) The questions ordinarily discussed in real logic constitute for us the object of a treatise which comes next after psychology, and which we call criteriology (science of the criterion of truth and certitude), or analysis of certain knowledge.

(2) Formal logic is generally divided into three parts, treating respectively of apprehension, of judgment, and of reasoning. This division, which is unimpeachable, is borrowed from the material object of logic. Without rejecting it, we prefer:

(3) Another division, which squares better with the general distribution of every philosophic study^{2} and is inspired by the study of logical order by its four causes, efficient, material, formal and final.^{3}

The study of the efficient cause of logic belongs, properly speaking, to psychology. Here it forms the object of a Preliminary Chapter (Chap. I). The First Part of the treatise on logic will have for its object concepts and terms, the materials of logical order: The Material Cause of logical order (Chap. II).

The Second Part will have for its object the arrangement of these materials, their deliberate disposition in judgments, reasoning, system, to secure the knowledge of truth: Formal Cause of logical order (Chap. III).

A concluding chapter will have for its object the employment of rational order in the service of science and philosophy: Final Cause of logical order (Chap. IV).^{4}

{1} See Criteriology, no. 42.

{2} Cf. the beginning of an opusculum in logic reckoned among the works of St. Thomas: De totius Logicae Aristotelis Summa. Op. XLIV, Procemium. Ed. Parm.

{3} Cf. General Metaphysics, fourth part.

{4} These four causes of logical order are mentioned in the definition of logic [1] and in the text of St. Thomas: Logic is the "art by which the act of the reason itself [material cause] may be directed [formal cause], by which man [efficient cause] may proceed easily and correctly in the very act of reasoning [final cause]."